The present invention relates to a dynamic seal between a rotating part and a stationary part where at least one of the parts is provided with projections which protrude into the seal gap.
In particular in the instance of vacuum pumps there frequently exists the requirement of having to seal shafts which penetrate a separating wall between two chambers at different pressures. Commonly, labyrinth seals are employed to this end, as is also known from U.S. Pat. No. 3,399,827, for example.
In the instances of seals for gaps extending approximately radially it is known (c.f. U.S. Pat. No. 5,165,872, gap seal 43 in FIG. 5) to employ purge gases (nitrogen, argon or alike) to protect, for example, a bearing/motor chamber against the ingress of detrimental gases. The purge gas is admitted into the bearing/motor chamber and passes through the seal for the gap into the pump chamber so that it is ensured that gases can not pass from the pump chamber into the motor chamber.
It is the task of the present invention to create an effective dynamic seal for gaps extending approximately radially between a rotating and a stationary component. This task is solved through the characterizing features of the patent claims.
Through the employment of projections designed by way of engaging rows of blades, not only can the desired sealing effect be improved; moreover, there exists the possibility of assigning to the seal pumping properties beneficial to the application in each instance. If, for example, a chamber is to be protected against the ingress of gases, the rows of blades, respectively the angle of incidence for the blades forming the rows of blades, may be so selected that the seal provides a pumping action in a direction opposed to the direction of the flow of the detrimental gases.
Still further advantages of the present invention will become apparent to those of ordinary skill in the art upon reading and understanding the following detailed description of the preferred embodiments.